1. Field of the Invention
The invention relates in general to an organic light emitting diode (OLED) display panel, and more particularly to an OLED display panel having a continual-piece conductive layer corresponding to an opening of the display region disposed between the thin film transistor (TFT) and the substrate.
2. Description of the Related Art
OLED display panel can be driven to emit via current driven or voltage driven without using a backlight source as ordinary liquid crystal display (LCD) panel would require. Thus, the OLED display panel has the advantages of self-luminance, wide view-angle, and full colors. Moreover, the OLED display panel can further be applied to portable electronic devices, such as mobile phone and personal digital assistant (PDA) for instance, and has become a display panel with great potentials.
Conventional OLED display panel includes an upper substrate, a lower substrate, an active matrix pixel array, several first thin film transistors (TFTs), several second TFTs and several organic electroluminescent devices (OELDs). The upper substrate and the lower substrate are assembled in parallel via the sealant. The active matrix pixel array is disposed above the upper substrate and positioned between the upper substrate and the lower substrate. The active matrix pixel array includes several pixels. Each pixel is defined by a first scan line and its adjacent second scan line as well as a first data line and its adjacent second data line both of which are disposed on the lower substrate. The first TFTs and the second TFTs are disposed inside the non-display regions of the pixels. Each second TFT is electrically connected to the corresponding first scan line, the first data line and the first TFT The organic electroluminescent devices are disposed inside the display regions of the pixels. Each organic electroluminescent device is electrically connected to the corresponding first TFT, a first voltage and a second voltage.
Each first TFT includes a channel layer, a gate, a source and a drain. The channel layer is disposed above the lower substrate. The source and the drain are disposed above the channel layer and respectively contact with the two opposite sides of the channel layer. The gate is disposed above the channel layer and positioned between the source and the drain. The above organic electroluminescent device is electrically connected to the drain for receiving the current outputted from the source via the channel layer and emitting according to the magnitude of the current.
However, when static charges are attached to the outer surface of the lower substrate or an external electric field is generated to the lower substrate, the static charges or the external electric field would result in extra vertical electric field interference to the channel layer of the second TFT, severely affecting the operation of the second TFT and further changing the current flowing through the channel layer. Especially, when the lower substrate becomes thinner, the unexpected and undesired interference of the electric field to the channel layer would be further intensified. Therefore, undesired luminance change would occur to partial pixels of the display region of the OLED display panel, largely reducing the display quality of OLED display panel.